G.fast is an ITU (International Telecommunication Union) DSL (digital subscriber line) standard, providing ultra-high-speed broadband network transmission. The service distance of G.fast is within 300 m, which provides a solution to the last mile problem for broadband networks. Therefore, in places where optical fiber deployment is difficult and copper wires are used to connect residences, G.fast can achieve ultra high bandwidth and speed. For example, the network transmission speed of the copper telephone wire in an old traditional building can be increased up to 1 Gbps. The usage of the G.fast system does not require rewiring in the entire building or homes. Thus, the most expensive and time-consuming process for connecting the optical fiber to residences can be eliminated. At the same time, the digital subscriber line access multiplexer (DSLAM) of VDSL is already installed widely in the field as an existing broadband service to provide transmission speeds of up to 100 Mbps. A telecommunications company may use the same bundle of wires for G.fast service, but crosstalk occurs when G.fast and VDSL services both use the same bundle of wires.
Please refer to FIG. 1, which is an installation scenario for installing VDSL and G.fast on the same bundle of wires. FIG. 1 shows G.fast distribution point unit (DPU)/DSLAM equipment 101 which has many ports. Some of the ports of G.fast DPU/DSLAM equipment 101 (3 ports are shown in FIG. 1) are each connected to an individual unit of G.fast customer premises equipment (CPE) 103. The other side of G.fast DPU/DSLAM equipment 101 is connected to an optical fiber or an optical line terminal (OLT) 105, and to the Internet 106, a video on demand server 107 and an element management system (EMS) server 108 through the optical fiber or the optical line terminal (OLT) 105. Each of the ports of G.fast DPU/DSLAM equipment 101 is connected to an individual unit of G.fast CPE 103 through a telephone line (where each telephone line consists of a pair of copper wires) 109-1, 109-2 or 109-3. A bundle of wires is already installed, and the bundle of wires includes many telephone lines wrapped up together. For example, the DSLAM 102 of VDSL and CPE 104 of VDSL are connected by a telephone line 109-n in the bundle of wires. The telephone lines 109-1, 109-2 and 109-3 for the G.fast system, and the telephone line 109-n for VDSL are all part of the bundle of wires.
If VDSL and G.fast are installed through the same DSLAM, near end crosstalk (NEXT) and far end crosstalk (FEXT) vectoring technologies can be used to solve the crosstalk interference issue. But if G.fast is installed after VDSL, the DSLAMs will be different, and these vectoring technologies cannot remove the crosstalk.
In addition, because G.fast DPU/DSLAM equipment is typically installed after the installation of VDSL service, it is mandatory to remove crosstalk between VDSL and G.fast when G.fast DPU/DSLAM equipment is installed. The maximum aggregate transmit power for G.fast is 4 dBm and this is lower than that of existing VDSL technology. As a result, G.fast suffers enormous interference from various types of VDSLs. VDSL can cause speed drops, packet loss, and even worse, causing the G.fast link to go down.
G.fast has two profiles corresponding to bandwidths (maximum frequencies) of 106 MHz and 212 MHz. VDSL has many profiles, e.g. 8a, 8b, 8c, 8d, 12a, 12b, 17a and 30a, each with its own bandwidth. Among them, 30a has the largest bandwidth (highest maximum frequency) of 30 MHz. The existing VDSL service on the bundle of wires may include one or more of the profiles above. ITU Recommendation ITU-T G.9700 requires that the G.fast system be equipped with a set of tools called a power spectral density (PSD) mask, which can be configured to deal with the problem of crosstalk interference between VDSL and G.fast. For example, a PSD mask can be configured to set a start frequency in the G.fast system so that the frequency range of the G.fast system lies outside those of all the existing VDSLs on the bundle of wires which cause crosstalk, thus removing crosstalk automatically. The set of tools can also be used to set a minimum G.fast frequency, e.g., 2.2 MHz.
For the convenience of the installation technician who configures the start frequency in the G.fast system corresponding to each port of G.fast DPU/DSLAM equipment, the G.fast DPU/DSLAM equipment manufacturer usually provides G.fast DPU/DSLAM equipment with the following functions: measuring a type of loop diagnostic metric data related to a communication loop connected between a port of G.fast DPU/DSLAM equipment and CPE, e.g., signal-to-noise ratio (SNR), and showing the loop diagnostic metric data to the installation technician so he can determine the start frequency in the G.fast system corresponding to the port. Therefore, the installation technician has to be able to read the loop diagnostic metric data, determine the start frequency in the G.fast system, and set the start frequency using his knowledge of the G.fast system and equipment. However, typical installation technicians do not have these abilities. Experienced technicians with these abilities have to be dispatched, leading to high operation cost. However, even for experienced technicians with these abilities, to manually complete all the work related to setting the start frequency in the G.fast system corresponding to one port, approximately one to two hours are needed. To install one unit of G.fast DPU/DSLAM equipment usually means setting the start frequencies in the G.fast system corresponding to multiple ports plus related work including testing, which causes the average installation time of a unit of G.fast DPU/DSLAM equipment to be about two days. The lengthy installation time is detrimental to the promotion of G.fast, not to mention that manual operations may introduce misjudgments, e.g., in determining the start frequency in the G.fast system, or in setting the start frequency. Therefore, an invention which can greatly speed up the installation time and facilitate the correct installation by typical installation technicians is urgently needed.
In order to overcome the drawbacks in the prior art, a method and an apparatus for automatically removing crosstalk is disclosed.